Dexterous manipulation from pinching to power grasping - strategy selection according to object dimensions and grasping position

Abstract

This paper discuses practical strategies for transition from a pinching to a power grasping, where a multi-fingered hand monnted on a robotic arm envelops a cylindrical object on a table. When the manipulation system grasps a cylindrical object like a pen on a desk, a complete enveloping is not impossible in the initial configuration. The system firstly pinches the object only with two or three fingers and then grasp it with fingers and a palm after regrasping. In this pinching-grasping transition maneuver, human unconsciously selects proper strategy according to some conditions including object dimensions and initial pinching positions. In this paper we therefore develop six possible strategies for this pinchinggrasping transition and then investigate their performances for some objects with various dimensions and various grasping positions, using numerical simulations. Based on their results, a strategy selection algorithm for these conditions is proposed and some experiment results are shown.